A variety of different methods and machines have been developed to extract mineral and fossil fuels at and below the earth's surface. Typically, cutting machines have been developed to maximise excavation recovery and drilling efficiency. In particular, within a mining environment, a variety of different machines have been developed for specific purposes. Whilst some machines are configured exclusively to cut mineral from a deposit or rock, other machines are configured to tunnel within the subterranean depth to effectively create the mine and provide passageways for the mineral cutters. Mobile mining machines typically comprise a rotatable cutting or mining head having cutting bits provided on rotating drums that contact the rock face. As the cutting head is rotated and advanced into the seam, the extracted mineral is gathered by a gathering head and then conveyed rearwardly by the machine via a conveying apparatus. Conventionally, water spray nozzles are mounted at the cutting head adjacent each cutting bit to suppress the generation of airborne dust that would otherwise pollute the environment surrounding the mine and present a frictional ignition medium. Water is fed continuously to the spray nozzles during head rotation for instantaneous dust suppression. The water spray is further advantageous to reduce frictional contact between the material deposit and the cutting bits so as to extend the bit lifetimes. The water supply network typically comprises one or a plurality of fluid control valves to control the high pressure water delivery to each bit optionally by a pulsing supply action. Example water supply systems and valve arrangements are described in GB 1,110,763; EP 0111143; DE 386651, U.S. Pat. No. 4,721,341; GB 2333548 and U.S. Pat. No. 6,070,944.
Percussion drilling is a well-established technique that breaks rock by hammering impacts transferred from a rock drill bit mounted at one end of a drill string to the rock at the bottom of a borehole. The fragmented rock pieces are flushed rearwardly along the borehole by a flushing fluid that is controlled and supplied via a pressurised fluid delivered to the drill bit. One or more valves are provided at the delivery end of the fluid network to control the supply of pressurised fluid. Example fluid supply networks are described in U.S. Pat. No. 8,061,434 and U.S. Pat. No. 4,852,947.
However, conventional fluid control valve arrangements are disadvantageous for a number of reasons. In particular, the control valves are typically hydraulically actuated via a piston and plunger arrangement and it is not uncommon for seals that partition the water network from the oil network to fail resulting in contamination of one or both circuits. Additionally, working components of the valve are commonly exposed to the fluid supply network and degrade or become impeded by particulates within the water circuit that inhibit valve performance. Furthermore, conventional valve arrangements are generally bulky so as to withstand the harsh working environments typically associated with miners or dust laden environments. Where a plurality of control valves are utilised within a fluid network, the overall size of the valve assembly is often prohibitive for convenient mounting at a mobile mining or cutting machine. Accordingly, what is required is a valve and valve assembly to form part of a fluid supply network that addresses the above problems.